Methods and apparatuses for notifying an application function of resource restrictions relating to a communication session

ABSTRACT

The invention relates to a method of notifying an Application Function (AF) in a communications network of resource restrictions relating to a communication session. The network includes a Policy and Charging Rules Function (PCRF) for authorising and controlling flows of data in the session. In the method the AF sends an authorisation request to the PCRF for establishing the communication session. The authorisation request includes an indication that the AF is to be notified of resource restrictions for the data flows in the session. The PCRF notifies the AF of the resource restrictions.

TECHNICAL FIELD

The invention relates to methods and apparatus that enable userequipment to be notified of resource restrictions in a multimediacommunications network.

BACKGROUND

The IP Multimedia Subsystem (IMS) is the technology defined by the ThirdGeneration Partnership Project (3GPP) to provide IP Multimedia servicesover mobile communication networks. IP Multimedia services provide adynamic combination of voice, video, messaging, data, etc. within thesame session. As the number of basic applications, and the media whichit is possible to combine, increases, so will the number of servicesoffered to the end users, giving rise to a new generation ofpersonalised, rich multimedia communication services. The IMS is definedin the 3GPP Specification 23.228.

The IMS makes use of the Session Initiation Protocol (SIP) to set up andcontrol calls or sessions between user terminals (or user terminals andapplication servers). The Session Description Protocol (SDP), carried bySIP signalling, is used to describe and negotiate the media componentsof the session. Whilst SIP was created as a user-to-user protocol, IMSallows operators and service providers to control user access toservices and to charge users accordingly.

FIG. 1 illustrates schematically how the IMS 3 fits into the mobilenetwork architecture in the case of a GPRS/PS access network. As shownin FIG. 1 control of communications occurs at three layers (or planes).The lowest layer is the Connectivity Layer 1, also referred to as thebearer, or traffic plane and through which signals are directed to/fromuser terminals accessing the network. The GPRS network includes variousGPRS Support Nodes (GSNs) 2 a, 2 b. A gateway GPRS support node (GGSN) 2a acts as an interface between the GPRS backbone network and othernetworks (radio network and the IMS network). A Serving GPRS SupportNode (SGSN) 2 b keeps track of the location of an individual MobileTerminal and performs security functions and access control. Access tothe IMS 3 by IMS subscribers is performed through an IP-ConnectivityAccess Network (IP-CAN). In FIG. 1 the IP-CAN is a GPRS networkincluding entities linking the user equipment to the IMS 3 via theconnectivity layer 1.

The IMS 3 includes a core network 3 a, which operates over the middle,Control Layer 4 and the Connectivity Layer 1, and a Service Network 3 b.The IMS core network 3 a includes nodes that send/receive signalsto/from the GPRS network via the GGSN 2 a at the Connectivity Layer 1and network nodes that include Call/Session Control Functions (CSCFs) 5.The CSCFs 5 include Serving CSCFs (S-CSCF) and Proxy CSCFs (P-CSCF),which operate as SIP proxies within the IMS in the middle, ControlLayer.

At the top is the Application Layer 6, which includes the IMS servicenetwork 3 b. Application Servers (ASs) 7 are provided for implementingIMS service functionality. Application Servers 7 provide services toend-users on a session-by-session basis, and may be connected as anend-point to a single user, or “linked in” to a session between two ormore users. Certain Application Servers 7 will perform actions dependentupon subscriber identities (either the called or calling subscriber,whichever is “owned” by the network controlling the Application Server7).

These session-based applications enable one or more users to participatein interactive user sessions such as video, voice, chat, gaming andvirtual reality sessions. The IMS architecture also makes it possible todeploy peer-to-peer applications where two or more users exchange dataduring a SIP session. Examples of such peer-to-peer applications includeMultimedia Telephony (MMTel), Push to Talk over Cellular (PoC),streaming, real-time video sharing, file sharing, gaming etc. Thetransport connection(s) is (are) negotiated dynamically by means of theSIP/SDP protocol exchange between the two end points (user terminals).

However, in order to support such peer-to-peer applications, there aretwo basic requirements: (i) a mechanism is needed to selectively controlthe SIP signal flows associated with the IMS session(s) of a subscriber;and (ii) a functionality is needed to control the IP flows through thedynamically negotiated transport connections in order to apply aneffective charging for usage of services. One important aspect concernsthe resources required for the session, which will impact on the Qualityof Service (QoS) provided for the session (e.g. the data rate at whichdata is transferred between the end users). In the discussion below theterm QoS is used to refer to those parameters of a requested or on-goingsession that determine the Quality of the Service experienced by the enduser. The principal bearer resource affecting QoS is the availablebandwidth for the session.

The 3GPP has recognised these needs and has defined a Policy andCharging Control (PCC) Architecture (see 3GPP Technical Specification23.203). FIG. 2 presents the basic outline of the PCC architecture. TheApplication Function (AF) 16 is an element offering applications thatrequire dynamic policy and/or charging control of traffic planeresources. Although the application services are initiated and servicecharacteristics are negotiated at the Application Layer 6 (e.g. by anApplication Server 7—see FIG. 1), a CSCF 5 (the P-CSCF) plays the roleof the AF 16 at the SIP signalling plane (Control Layer 4). A Policy andCharging Enforcement Function (PCEF) 12 in the Connectivity Layer 1monitors service data flow and enforces network policy. The PCEF 12 alsoapplies charging based on the monitored data flow and the chargingpolicy applied. This information is provided to an Online ChargingSystem 13 over the Gy interface. As shown in FIG. 2, the PCEF 12 iscontained within the access gateway node. Within a GPRS access network,the PCEF 12 is located in the GGSN 2 a. Within the Systems ArchitectureEvolution defined in 3GPP Release 8, the PCEF is located in the PublicData Network (PDN) gateway.

A Policy and Charging Rules Function (PCRF) 14 resides in between the AF16 and the PCEF 12. The PCRF 14 is the entity that controls chargingbased on the monitored data flow. The PCRF 14 obtains rules relating tothe charging policy to be applied for particular subscribers over the Spinterface from a Subscription Profile Repository (SPR) 18, whichincludes a database of subscriber information. The PCRF 14 installsthese PCC rules at the PCEF 12 over the Gx interface. These ensure thatonly authorized media flows associated with the requested services areallowed. In addition, the PCC rules installed at the PCEF 12 ensure thatthe right bandwidth, charging and priority are applied through the rightbearer.

Once session characteristics are negotiated between the communicationpeers and the session characteristics are authorized within the IMS CoreNetwork 3 a, the AF 16 provides an authorization of bearer resourcesover the Rx interface to the PCRF 14 so that the corresponding resourcereservation can be authorized at the Connectivity Layer 1. The PCCarchitecture is used to control the bearer resources and thus guaranteethat services are delivered with the right quality—i.e. the qualityrequired for the particular services provided, but also in accordancewith the user's access subscription and access operator policies. IP-CANoperators normally apply bandwidth limits in terms of the concurrentbandwidth available to their users at a given moment in time (e.g. 200kbps bit pipe). Access operators may also limit the bandwidth availablefor certain access technologies (e.g. for UTRAN access, the maximumbandwidth allowed is 80 kbps). Access network operators may also limitthe number of concurrent bearers/services available to their users. Whenthese limitations are reached and the quality for the service cannot beguaranteed, the PCC architecture will reject the bearer resources forthe service. In this PCC configuration, the PCRF will inform the AF ofthe reason for the rejection so that it can take appropriate action(e.g. reject the session, re-negotiate the session, etc.). In scenarioswhere an AF is not present (Rx is not used), the PCRF will downgrade oreven reject a bearer establishment or modification attempt from the UE.

However, these limitations are controlled and managed by the accessnetwork (IP-CAN) operator, meaning that the UEs and clients are notaware of them. The UEs in use today include many that support advancedcapabilities such as the use of the most up-to-date codecs. In thefuture UEs will be able to support still more advanced capabilities.These UEs will try to initiate services making use of the highestcapabilities they support. For example, an IMS client's UE will normallyattempt to initiate a session by offering all the codecs it supports(unless manually configured otherwise), ignoring any bandwidthlimitation set by the access operator. Similarly, users may also try torun a number of services on their terminals concurrently. For example, auser may want to download e-mail and transfer files using File TransferProtocol (FTP) at the same time as having an MMTel video call. In thiscase, the UE may attempt to establish multiple bearers. The number ofbearers that can be active simultaneously is, on the one hand limited bythe UE manufacturer's implementation (i.e. the terminal is capable ofhandling a maximum number of concurrent bearers). On the other hand,there may be a limit imposed by the network on the number of bearers auser is allowed to establish, regardless of the capabilities of theterminal.

In summary—network-based mechanisms are used to control the usage ofresources for a session, but UEs may try to maintain multiple concurrentservices making use of their most advanced capabilities. This willfrequently result in additional control signalling. At the applicationlevel a round of Request and Reject control messages may be followed bya re-attempt of the original request using different characteristics(e.g. downgrading of QoS with a request for lower bandwidth, lessdemanding codecs or restricting use of particular media-types) to tryand establish a session without exceeding the access operator'sestablished limits. At the bearer level there will either be a round ofRequest/Reject control signalling messages or a round ofRequest/Response messages (accepting a downgraded QoS) potentiallyfollowed by a bearer termination if the QoS downgrade is not acceptablefor the service delivery.

The present invention has been conceived with the foregoing in mind.

SUMMARY

According to a first aspect of the present invention there is provided amethod of notifying user equipment, UE, accessing an IP ConnectivityAccess Network, IP-CAN, of network resource restrictions. The IP-CANauthorises and controls the provision of network services to the UE. Inthis method a message originating from the UE is received in the IP-CAN.In response to this message the IP-CAN sends a reply that includesresource restriction information applicable to the provision of networkservices involving the UE. The resource restriction information is thenforwarded to the UE.

The resource restriction information may comprise information about theIP Connectivity Access Network, IP-CAN restrictions that apply. Theresource restriction information may comprise bandwidth constraints peruser and/or bandwidth constraints per IP-CAN technology type, and/or themaximum number of concurrent bearers per user, and/or the maximum numberof concurrent bearers per IP-CAN technology Type and/or any otheroperator defined restrictions for the use of IP-CAN resources.

It is an advantage that the UE is provided with information about theIP-CAN restrictions set by the access operator so that it can startapplication sessions and bearer procedures with a high degree ofsuccess. In other words, service invocations initiated by the UE willnot be rejected, at least not due to IP-CAN resource restrictions beingexceeded.

It is a further advantage that the resource restriction information canbe conveyed to the UE within current IP-CAN session establishmentprocedures—for example by making use of the Protocol ConfigurationOption (PCO) parameter.

Once this information is available in the UE, the UE (maybe assisted bythe actual user), is able to adapt service requests so that they fallwithin the received bandwidth limits (e.g. by requesting less bandwidth,requesting less demanding codecs or restricting use of particularmedia-types) and/or other IP-CAN session restrictions. The UE may alsochoose to downgrade or terminate some of the existing flows to make roomfor the new service request.

In embodiments of the invention, the IP-CAN comprises a Policy andCharging Rules Function, PCRF, for controlling access operator policiesand determining the resource restrictions that apply within the IP-CANto the user of the UE.

In embodiments of the invention, the method further comprises notifyingthe UE of up-dated resource restrictions in an IP-CAN sessionmodification request initiated by the IP-CAN or in a response to anIP-CAN session modification request initiated by the UE. Where theIP-CAN is a GPRS network, the IP-CAN session establishment andmodification commands may correspond to UE or GGSN initiated PDP Contextrequest/modification procedures that comprise a Protocol ConfigurationOption (PCO) parameter, which is used to convey the resource restrictioninformation.

In embodiments of the invention, the resource restriction informationmay be sent to the UE using application level signalling procedures froman Application Function. The Application Function may receiveinformation relating to resource restrictions in the response of anAuthorization Request or in an Re-Authorisation Request received fromthe PCRF over the Rx reference point. The Application Function may becomprised in a Proxy-Call Session Control Function, P-CSCF and theresource restriction information may be pushed down to the UE during SIPregistration and re-registration procedures.

In another embodiment the resource restriction information is forwardedto the UE from a Profile Delivery Server, PDS, using SIP signalling. ThePDS may be comprised in a Proxy-Call Session Control Function, P-CSCF.The PDS may obtain the resource restriction information from the PCRF orthe PDS may be comprised in a PCRF. The UE may subscribe to the PDS toreceive notifications of changes of the IP-CAN restriction information.

In embodiments of the invention the PCRF retrieves the resourcerestriction information from a memory in the PCRF before sending thereply, or retrieves the resource restriction information from anothersource, for example a Subscription Profile Repository, SPR.

Preferably, the method further comprises storing the resourcerestriction information at the UE.

According to a second aspect of the present invention there is provideda method of invoking or accepting service requests provided by an IPcommunications network to a user equipment, UE, accessing the network.In this method, the UE has already been provided with informationrelating to applicable network resource restrictions. The methodincludes checking the resource restrictions to ascertain a Quality ofService, QoS, that complies with the restrictions for a desired servicerequest, and then generating, or responding to, a service requestmessage that includes a specification of resources for the QoS. Theservice request or response message is then sent to the network.

The specification of resources for the QoS may comprise servicecharacteristics that lie within the restrictions established for theIP-CAN. When after checking the resource restrictions the UE is unableto ascertain a QoS that complies with the restrictions, the UE eitherabandons the attempt to invoke or accept a service request, or adjuststhe QoS of the service request by determining a revised set of QoSparameters that comply with the restrictions. The revised set of QoSparameters may be determined either by a Mobile Terminal in the UE, theMobile Terminal establishing or modifying IP-CAN bearers according toQoS characteristics that lie within the IP-CAN restrictions, or by aclient application in the UE 10, which adjusts the session request sothat it complies with the IP-CAN restrictions. The UE may revise the QoSparameters on the basis of prioritised services, the revision of QoSparameters comprising downgrading or terminating one service in favourof another based on the service priorities. The UE may either prioritisethe services based on pre-configured user preferences, or poll the userto determine the prioritisation of services.

According to a third aspect of the present invention there is providedUser equipment, UE, configured to participate in a communication sessionby accessing an IP-CAN. The IP-CAN authorises and controls the provisionof network services to the UE, and applies resource restrictions to theservices provided to the UE. The UE comprises a processor and atransceiver for sending messages to and receiving messages from thenetwork. The UE is configured to: generate and send a request message tothe network; receive from the network a reply in response to the requestmessage, wherein the reply comprises information identifying theresource restrictions applicable to the UE; and generate a request forthe provision of a service in accordance with the resource restrictions.

The UE preferably comprises a mobile terminal and one or more clientapplications. Preferably, the UE further comprises a memory for storingthe information identifying the resource restrictions, and the processorchecks the resource restriction information in the memory to ascertain arevised set of QoS parameters that comply with the restrictions. Thememory in the UE may comprise a store of prioritised services to be usedas a basis for ascertaining the revised QoS parameters.

According to another aspect of the present invention there is provided aPolicy and Charging Rules Function, PCRF, in an IP communicationsnetwork configured to authorise and control the provision of networkservices to UEs communicating over the network. The PCRF includes: meansfor receiving a message indicating that a UE is requesting notificationof network resource restrictions applicable to services provided to theUE; means for identifying the network resource restrictions; and meansfor sending a message comprising information identifying the resourcerestrictions.

The message indicating that the UE is requesting the resourcerestriction information may correspond to either a DiameterAuthorization Request received over a Rx reference point or a DiameterCharging Control Request received over a Gx reference point. The messagecomprising information identifying resource restrictions may correspondeither to a Diameter Re-Authorisation Request sent over a Rx or Gxreference point or a Diameter Charging Control Answer sent over the Gxreference point.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described below with reference to thedrawings, in which:

FIG. 1 is a schematic illustration of a GPRS/PS access network showinghow the IMS fits into the mobile network architecture.

FIG. 2 is a schematic illustration of the network entity architecture aPolicy and Charging Control (PCC) system.

FIG. 3 is an illustration of the signal flows between a UE and PCCentities in accordance with one embodiment of the invention.

FIG. 4 is an illustration of the signal flows between a UE and PCCentities in accordance with another embodiment of the invention.

FIG. 5 is an illustration of the signal flows between a UE and PCCentities for an example showing how the UE handles service invocationsin accordance with the invention.

DETAILED DESCRIPTION

FIG. 3 illustrates the signal flows between the PCC nodes (as shown inFIG. 2) for a user terminal (UE) 10, such as a mobile terminal, whichhas registered with the IMS via an IP Connectivity Access Network(IP-CAN). At step 301, the UE attempts to connect to the IP ConnectivityAccess Network (IP-CAN) by sending a Session Establishment Request tothe IP-CAN, which is received at the PCEF 12. For a GPRS IP-CAN (asshown in FIG. 1), the PCEF 12 is the GGSN 2, and this UE requestcorresponds to a first PDP Context request. A PDP (Packet Data Protocol)Context is a logical association between a UE or Mobile Terminal and aPDN (Public Data Network) running across a GPRS network. The PDP Contextdefines aspects such as Routing, QoS (Quality of Service), security,billing etc. At step 302 the PCEF 12 sends a Diameter Charging ControlRequest (CCR) message to the PCRF 14 over the Gx reference point (asdefined in 3GPP TS 29.212). This includes the IP address of the UE 10requesting the session, and according to this embodiment it alsoincludes a request to be provided with IP-CAN restriction information.

In this embodiment, the PCRF 14 manages the access operator policies,including the restrictions that apply to the usage of IP bearerresources. In one embodiment the PCRF 14 includes a memory storing theIP-CAN restriction information. Thus, at step 303, the PCRF 14 retrievesthe restriction information from its memory. In another embodiment, thePCRF is configured, on receiving the request for IP-CAN restrictioninformation, to retrieve this information at step 303 from anothersource, for example the SPR 18 (see FIG. 2).

At step 304, the PCRF returns a Diameter Charging Control Answer (CCA)message to the PCEF. The CCA message, as currently configured, includesthe pre-defined PCC rules that apply to the IP-CAN session. In addition,in accordance with this embodiment, the CCA message includes informationabout the restrictions that will apply to the IP-CAN Session. Theseinclude the bandwidth constraints (BCM) as well as the information aboutthe IP-CAN restrictions, as requested and retrieved by the PCRF 14.

At step 305, the PCEF 12 sends an IP-CAN Session Establishment Responseto the UE 10. This makes use of the Protocol Configuration Option (PCO)parameter, which is an existing parameter within IP-CAN sessionestablishment procedures. According to this embodiment the IP-CANrestriction information is included in the IP-CAN Session EstablishmentResponse using this PCO parameter.

At step 306 the UE stores the information it has received in the IP-CANSession Establishment Response relating to the IP-CAN restrictions. TheUE is then in a condition to make use of this information, as will bedescribed in more detail below.

Examples of the information on IP-CAN Restrictions provided to the UEfollowing the procedures described above include (but are not limitedto):

-   -   Bandwidth consumption limit per user;    -   Bandwidth consumption limit per IP-CAN access Technology        type—e.g. different limitations that apply for IP-CANs operating        in GPRS, GERAN (GSM-EDGE Radio Access Network), I-WLAN (Internet        Wireless Local Area Network), DOCSIS (Data Over Cable Service        Interface Specifications), etc.;    -   Maximum number of concurrent bearers (per user/access);    -   Other operator defined restrictions for the use of the IP-CAN        Resources.

Mind that, within current procedures, the GPRS network operator alreadyhas some control of the maximum number of concurrent bearers (PDPContexts in GPRS). The supported PDP Contexts for each subscriber areprovided by the Home Location Register (HLR) to the SGSN 2 b (seeFIG. 1) as part of the procedure when the mobile terminal attaches tothe network. The HLR may also specify a maximum number of PDP contextsper subscriber. The SGSN 2 b can also set, as a configuration parameter,the maximum number of active PDP contexts it can handle per subscriberbased on the SGSN's performance capabilities. However, the operatormight still want to limit the maximum number of concurrent PDP contextfor a particular user based on a dynamic policy control (e.g. based ontime of the day) below these rather static restrictions controlled bythe HLR and/or SGSN.

In general, the IP-CAN restrictions that the network has informed the UEabout during the IP-CAN session establishment are calculated byanalyzing certain conditions that do not change very frequently. Forexample, there can be physical limitations in certain access networks,which mean that the access operator cannot provide more than a certainbandwidth for the IP-CAN session. Subscription data is another factor(e.g. the maximum bandwidth for a subscriber can be dependent on theuser category). Although these conditions are not expected to changevery often, they can be modified (e.g. the physical conditions couldvary if, for example, the user is roaming to a different IP-CAN).Therefore, when changing conditions require the IP-CAN session to bemodified, the PCRF will have to determine if the IP-CAN restrictionshave been changed and then inform the UE.

In this embodiment, the same PCO-based mechanism that was used duringthe IP-CAN session establishment is also used to provide the UE withupdates to the IP-CAN restrictions. Thus, for GPRS networks the PCOparameter is used to send information about the new restrictions to theUE within a GGSN initiated PDP-Context-Modification Procedure.

Following the approach within this embodiment, the mobile terminal (MT),which takes care of the bearer resources within the UE, provides theIP-CAN Restriction information to the different client applicationsresiding within the UE 10. Moreover, the client applications residing inthe UE 10 will have to determine whether or not the service can beexecuted within the limits imposed by IP-CAN resource restrictions inthe bearer layer. If the service cannot be guaranteed within theresource restrictions, the client applications within the UE 10 willdecide the specific action to take (e.g. rejection of this or anotherservice, or provide a choice of services to the user, etc). Thisrequires that the interface between the MT and the client applicationswithin the UE allows the authorization of service requests according tothe usage restrictions of IP-CAN resources in the bearer layer. Forthose services that require certain characteristics negotiation betweenthe user and the application that depends on the available resources,the MT part of the UE shall provide acceptable QoS characteristics torun the service so the client application can adjust the requestaccordingly.

FIG. 4 illustrates an alternative method of providing the UE withinformation about the IP-CAN restrictions set by the access networkoperator. Instead of providing the information to the UE via IP-CANsignalling procedures as in the previously described embodiments, inthis embodiment the IP-CAN restriction information is sent to the UEusing Application level signalling procedures (e.g. SIP).

In the embodiment shown in FIG. 4, IP-CAN Restriction information ispushed down to the UE during the SIP Registration process. At step 401,the UE sends the initial SIP Register message to register in the IMS.This is routed to the P-CSCF (which, as explained above, also acts asthe AF 16 within the PCC infrastructure). At step 402, the P-CSCFforwards the SIP Register message to the IMS and at step 403, the P-CSCFreceives a SIP 200OK response message. Steps 401 to 403 are the normalsignal flows for registering the UE in the IMS. Normally at this pointthe P-CSCF would forward the 200OK message to the UE notifying it of asuccessful registration. However, in this embodiment of the invention,at step 404, the P-CSCF/AF 16 sends a Diameter Authorisation Request(AAR) message to the PCRF over the Rx interface. At step 405, the PCRFreplies with an Authorisation Answer (AAA) message. The AAA messageincludes information, regarding the IP-CAN resource restrictions. As inthe FIG. 3 embodiment, the PCRF either retrieves the information fromwithin a memory in the PCRF, or retrieves it from another source, forexample the SPR 18 (see FIG. 2). At step 406, the AF 16 (the IMS P-CSCF)sends the 200OK message, including the information about IP-CAN relatedpolicy restrictions within the 200OK successful response.

The benefit of this embodiment is that IP-CAN restriction informationcan be provided to the UE regardless of the type of IP-CAN. It alsoavoids internal checking of IP-CAN Restrictions within the UE (i.e.between client applications and the mobile terminal part of the UE) asthis information is directly received at the application layer withinthe UE. The IP-CAN restriction information might be limited in this caseto bandwidth limitations as the IMS applications platform within the UE10 should not need to be aware of other IP-CAN restrictions (forexample, the number of maximum concurrent bearers) unless internalinterfaces are opened between the application and IP bearer platformswithin the UE as proposed in a previous embodiment.

Referring again to FIG. 4, in this embodiment the PCRF notifies theAF/P-CSCF 16 of updated IP-CAN Restriction information via the Rxinterface through Diameter Re-Authorisation Request and Answer (RAR/RAA)messages at steps 407 and 408. Later on when the UE re-registers withthe IMS by exchanging a SIP re-REGISTER and 200OK messages, as in steps409-411, the AF/P-CSCF 16 will be able to include the updated IP-CANRestriction Information received in step 407 in the 200OK message sentto the UE in step 412. UEs have to re-register with the IMS from time totime, and also when the UE is roaming to a different IP-CAN.

In another embodiment, the SIP User Agent (UA) residing in theend-user's UE obtains information about the IP-CAN Restrictions directlyfrom a Profile Delivery Server (PDS). The UA represents the IMS/SIPlayer within the UE, which manages the IMS applications and SIPsignalling in the UE. The Internet Engineering Task Force, responsiblefor developing Internet standards, in IETFdraft-ietf-sipping-config-framework-12, specifies means for SIP UAs tocommunicate directly with Profile Delivery Servers.

Accordingly, the UA can contact the PDS directly, and obtain informationfrom it about the configuration. For this embodiment, the configurationinformation includes the IP-CAN Restrictions. When the UA contacts thePDS for the first time, it informs the PDS that it subscribes tonotification (i.e. wishes to be notified) of IP-CAN restrictions in theconfiguration information it receives. In principle, the UA is able tocontact the Profile Delivery Server at any time in order to subscribe toand retrieve notification of changes of IP-CAN restrictions. However, itis also possible that this facility is only made available while theuser remains registered within the IMS System. Within the IMS and PCCarchitecture as shown in FIGS. 1 and 2, either the P-CSCF 5 b or aSIP-Enabled PCRF 14 can act as a Profile Delivery Server. If the P-CSCF5 b acts as the Profile Delivery Server, the PCRF 14 provides the IP-CANRestriction information to the P-CSCF 5 b using the same procedures asdescribed above in relation to FIG. 4 (via Rx AAR/AAA and RAR/RAAmessages).

This embodiment provides immediate updates of IP-CAN Restriction info tothe UE, and is much more efficient (i.e. faster and more frequent) thanthe method of the FIG. 4 embodiment where notification of the updatesmust wait for a re-REGISTRATION to take place.

The restrictions represent the limits of the IP-CAN resources that theuser can make use of for all the active services during an establishedIP-CAN session. The network will reject an attempt to initiate newservices if any of the IP-CAN restrictions are exceeded. Therefore, oncethe UE has obtained the IP-CAN restriction information it can use thisin subsequent requests for services to avoid requests being rejected.Examples showing how the UE makes use of the information are shown inthe signal flow diagram of FIG. 5.

At the outset, the UE 10 (comprising the different client applicationsand mobile terminal handling bearer resources within the UE 10) hasregistered in the IMS and has been made aware of the IP-CAN restrictionsin accordance with one of the methods described above. In addition tothe PCC nodes, the example shows two Application Functions, AF1 16 a andAF2 16 b, providing services to users.

At step 501 the user wishes to initiate a session using service 1 with abandwidth of 50 kbps. The UE 10 checks the IP-CAN restrictions and notesthat the available bandwidth is 100 kbps, which is OK. Thus, at step 502the UE sends an IP-CAN bearer establishment request to the PCEF 12. Thisis forwarded at step 503 in the form of a CCR message to the PCRF 14. Atstep 504, the PCRF checks that the request complies with the IP-CANrestrictions, and at step 505 responds with a CCA message to the PCEF12. At step 506, the PCEF 14 sends a successful session establishmentresponse to the UE 10.

At step 507, the user wishes to use another service, service 2, with abandwidth of 30 kbps. Service 2 is provided by the Application FunctionAF1 16 a. The UE 10, knowing the IP-CAN restrictions, checks these tosee that there is still 50 kbps of available bandwidth and so, at step508, sends a SDP Offer to AF1 16 a. The offer includes the specifiedbandwidth, as well as the codecs that the UE supports for this service.At step 509, the offer is negotiated using the established sessionnegotiation procedure. At step 510, AF1 16 a sends an AuthorisationRequest AAR message to the PCRF 14. At step 511, the PCRF 14 checks theIP-CAN restrictions, and because these have not been exceeded, sends apositive Authorisation Answer to AF1 16 a. AF1 16 a then sends a SDPanswer to the UE 10 at step 513, indicating that the requested service 2will be provided. At step 514, the PCRF 14 reserves the IP-CAN resourcesfor the UE 10.

Thus it can be seen that, when the user tried to initiate a new service,the UE checked to see that the proposed QoS to be requested did notviolate any of the restrictions set by the IP-CAN. In the example inFIG. 5, the UE checked whether the bandwidth requested was within theaccess operator restrictions for usage of IP-CAN Resources. However,there may also be other restrictions that would have needed to bechecked, for example: whether a corresponding bearer procedure fitswithin the limits set by the IP-CAN; and which offered codec would bemost suitable considering the available bandwidth.

If the restrictions are not exceeded, the UE 10 will initiate theestablishment of the new service in the usual manner. If any of therestrictions are exceeded, the UE will have the option to either abandonthe attempt to initiate the service, or adjust the service request sothat it complies with the IP-CAN restrictions, if that is possible.Continuing with the example of FIG. 5, at step 515 the UE 10 receives anSDP Offer from Application Function AF2 16 b, inviting the user to joina session. The SDP Offer indicates that the preferred QoS for thesession requires a bandwidth of 30 kbps with a choice of codecs. At step516, the UE 10 checks to see if this complies with the IP-CANrestrictions and notes that the available bandwidth is only 20 kbps(because 80 kbps is already reserved for other bearers). In this case,the UE 10 provides an indication that it can participate in the session,but only with a bandwidth of 20 kbps, and the chosen codec 1. In thisexample, at step 517, the UE sends an SDP answer to the AF2 16 bindicating the available bandwidth and chosen codec. The AF2 will thendetermine if the service can be provided at this reduced QoS. If this isacceptable, the required QoS Resources will be successfully authorizedin steps 518-520 and reserved in step 521 since session characteristicsnow lie within the limits established by the IP-CAN.

When the UE 10 checks the IP-CAN restrictions and discovers that thereis insufficient bandwidth for the QoS to be specified within a PDPContext Request or within an SDP offer/answer, according to thisembodiment, the UE will have the option to either:

-   -   abandon the idea to initiate or accept the service request (e.g.        by rejecting an incoming service request or not even attempting        the initiation of a new dedicated PDP context to run the        service); or    -   adjust the service requirements to the IP-CAN restrictions if        possible (e.g. by adjusting the session and media        characteristics before sending a service request or adjusting        the requested QoS parameters within the request of a dedicated        PDP context).

Another possibility is that the UE 10 could prioritize the services,favouring the new service request over other ongoing services. Forexample, it could decide that the service requested in the SIP INVITE itreceives at step 515 has a higher priority than either service 1 orservice 2. Accordingly, it could accept the SIP INVITE at the requestedbandwidth, and instead reduce the bandwidth, or abandon, one or other ofservices 1 and 2. If it is not acceptable for the new service requestedto have its QoS downgraded, the UE may terminate a lower priorityservice (e.g. service 1 or service 2) and proceed with the new one. Inthis case, the UE may prioritise the services based on pre-configureduser preferences (e.g. “drop any other service when I do not have enoughbandwidth for a new incoming MTSI call”).

Another alternative is to make the UE involve the actual user in thedecision. For example, if the user is participating in avideoconference, reading his mailbox and accessing a web page and thenreceives an incoming voice call, the UE can be configured to display apop-up message on the terminal screen providing a choice for the user toselect. For example, the pop-up message could say: “Not enough resourcesfor a new entry call. If accepted your explorer will be dropped.Accept/Deny”.

1. A method of notifying user equipment, UE, accessing an IPConnectivity Access Network (IP-CAN) of network resource restrictions,wherein the IP-CAN authorizes and controls the provision of networkservices to the UE, the method comprising: during establishment of asession between the UE and the IP-CAN, receiving an IP-CAN SessionEstablishment Request at a Policy Charging and Enforcement Function,(PCEF) in the IP-CAN, from the UE; in response to receipt of saidRequest, sending a request for IP-CAN restriction information from saidPCEF to a Policy and Charging Rules Function, (PCRF) and receiving inresponse, at the PCEF, resource restriction information applicable tothe provision of network services involving the UE; sending an IP-CANSession Establishment Response from the PCEF to the UE that includessaid resource restriction information applicable to the provision ofnetwork services involving the UE for the session; and storing saidresource restriction information at the UE.
 2. The method of claim 1wherein the resource restriction information comprises information aboutthe IP Connectivity Access Network, IP-CAN restrictions that apply,comprising bandwidth constraints per user and/or bandwidth constraintsper IP-CAN technology type, and/or the maximum number of concurrentbearers per user, and/or the maximum number of concurrent bearers perIP-CAN technology Type and/or any other operator defined restrictionsfor the use of IP-CAN resources.
 3. The method of claim 1 wherein theIP-CAN resource restriction information is forwarded to the UB by meansof a Protocol Configuration Option (PCO) parameter in response to anIP-CAN Session Establishment request.
 4. The method of claim 1 furthercomprising notifying the UE of up-dated resource restrictions in anIP-CAN session modification request initiated by the IP-CAN or in aresponse to an IP-CAN session modification request initiated by the UE.5. The method of claim 4, wherein the IP-CAN is a GPRS network and theIP-CAN session establishment and modification commands correspond to UEor Gateway General Packet Radio Service (GPRS) Support Node (GGSN)initiated Packet Data Protocol (PDP) Context request/modificationprocedures that comprise a Protocol Configuration Option (PCO)parameter, which is used to convey the resource restriction information.6. The method of claim 1 wherein the PCRF retrieves the resourcerestriction information from a memory in the PCRF before sending thereply, or retrieves the resource restriction information from aSubscription Profile Repository (SPR).
 7. A method of invoking oraccepting service requests at a user equipment (UE), accessing an IPConnectivity Access Network (IP-CAN), wherein the UE has been providedwith information relating to network resource restrictions applicable tothe UE for the duration of a session between the UE and the IP-CAN, themethod comprising: checking the resource restrictions to ascertain aQuality of Service (QoS) that complies with the restrictions for adesired service request; generating or responding to a service requestmessage that includes a specification of resources for said QOS; andsending said service request or response message to said IP-CAN.
 8. Themethod of claim 7, wherein the specification of resources for said QoScomprises service characteristics that lie within the restrictionsestablished for the IP-CAN, so that when after checking the resourcerestrictions the UE is unable to ascertain a QoS that complies with therestrictions, the UE either abandons the attempt to invoke or accept aservice request, or adjusts the QoS of the service request bydetermining a revised set of QoS parameters that comply with therestrictions.
 9. The method of claim 8 wherein the revised set of QoSparameters are determined either by a Mobile Terminal in the UE, theMobile Terminal establishing or modifying IP-CAN bearers according toQoS characteristics that lie within the IP-CAN restrictions, or by aclient application in the UE, which adjusts the session request so thatit complies with the IP-CAN restrictions,
 10. The method of claim 9wherein the UE revises the QoS parameters on the basis of prioritisedservices, the revision of QoS parameters comprising downgrading orterminating one service in favour of another based on the servicepriorities.
 11. The method of claim 10 wherein the UE either prioritisesthe services based on pre-configured user preferences, or polls the userto determine the prioritisation of services.
 12. An User equipment (UE)configured to participate in a communication session by accessing an IPConnectivity Access Network, IP-CAN, wherein the IP-CAN authorizes andcontrols the provision of network services to the UE and appliesresource restrictions to the services provided to the UE, the UEcomprising a processor and a transceiver for sending messages to andreceiving messages from the IP-CAN, the UE being configured to: generateand send a request message to the IP-CAN; receive from the network areply in response to the request message, wherein the reply comprisesinformation identifying said resource restrictions applicable to the UEfor the duration of the session; and generate a request for theprovision of a service in accordance with said resource restrictions.13. The User Equipment of claim 12 comprising a mobile terminal and oneor more client applications.
 14. The User Equipment of claim 12, furthercomprising a memory for storing said information identifying saidresource restrictions, wherein the processor is configured to check theresource restriction information in the memory to ascertain a revisedset of QoS parameters for said service that comply with therestrictions.
 15. The User Equipment of claim 14 wherein the memorycomprises a store of prioritised services, the processor ascertainingthe revised QoS parameters on the basis of said prioritised services.16. A Policy and Charging Rules Function (PCRF) in an IP communicationsnetwork configured to authorise and control the provision of networkservices to User Equipment (UEs) communicating over the network, andcomprising: means for receiving a message indicating that a UE isrequesting notification of network resource restrictions applicable toservices provided to the UE for the duration of a session between the UEand the IP communications network; means for identifying said networkresource restrictions; and means for sending a message comprisinginformation identifying said resource restrictions.
 17. The PCRF ofclaim 16 wherein the message indicating that a UE is requestinginformation of network resource restrictions applicable to servicesprovided to the UE corresponds to either a Diameter AuthorizationRequest received over a Rx reference point or a Diameter ChargingControl Request received over a Gx reference point.
 18. The PCRF ofclaim 16 wherein the message comprising information identifying saidresource restriction corresponds either to a Diameter Re-AuthorisationRequest sent over a Rx or Gx reference points or a Diameter ChargingControl Answer sent over the Gx reference point.